Conventional motors typically have a rotational portion (a “rotor”), a stationary portion (a “stator”) rotationally secured to the rotor, and circuitry that causes the rotor to rotate in a predetermined manner. Among other functions, the circuitry may produce a predetermined force that causes the rotor to begin rotating from an at rest position. This force often is referred to in the art as “starting torque.”
Undesirably, there are times when the starting torque of a motor is not strong enough to overcome its at rest inertia. For example, in automotive applications, it may be necessary for a small DC electric fan to start at very low temperatures (e.g., −40 degrees C.). In such case, frozen moisture on the motor bearing system may produce a large rotor drag that requires a very high torque to start the motor. If this high torque is greater than the starting torque, then the motor may not start rotating. In addition to this, a variety of other factors, such as humidity, dust, bearing grease, and mounting position also may produce a rotor drag that the starting torque cannot overcome.